Dosage compensation is the mechanism by which the amount of gene product from the X chromosomes is equalized in males and females despite the difference in gene (chromosome) number. Evolution has solved this dosage in several ways. In Drosophila melanogaster, the single x chromosome in the male is hypertranscribed resulting in exactly the same amount of gene product found in females (two X chromosomes). Our lab is interested in understanding the transacting factors (collectively called the male specific lethals or MSLs) that regulate this hypertranscription. Male flies, mutant for any one of the four msl's, die as larvae. Females of the same genotype are phenotypically normal. I will use classic genetics to look for suppressers of the msl phenotype and molecular genetics to characterize them. My other pilot project will focus on proteins that interact with the recently cloned msl-2, a RING-finger protein that localizes specifically to the X chromosome in males. It is the only one of the known msl's that is sex specifically spliced. I will use the yeast two hybrid system to look for proteins that interact with msl-2 and may therefore be involved in the dosage compensation process.